/*撑满整个父元素*/
@mixin full_parent {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
}


/*flex*/
@mixin flex_center($justify) {
    display: flex;
    @if($justify) {
        justify-content: $justify;
    }
    align-items: center;
}

